Ultrasonic subcutaneous dissection tool incorporating fluid delivery

ABSTRACT

Ultrasonic dissection instruments and methods provide for fluid delivery during subcutaneous dissection. An ultrasonic dissection tool includes a handle, a transducer and a dissecting member. The dissecting member extends from the distal end of the transducer, and a fluid channel system extends from at least the proximal end to the distal end of the dissecting member. The fluid channel system terminates in a port system. The port system may include one or more apertures, one or more channels, and be adapted to transport fluids such as, for example, irrigation fluids, fluids having analgesics, antibiotics, and combinations of fluids and agents.

RELATED APPLICATIONS

[0001] This application claims the benefit of Provisional PatentApplication Serial No. 60/462,272, filed on Apr. 11, 2003, to whichpriority is claimed pursuant to 35 U.S.C. §119(e) and which is herebyincorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates generally to ultrasonic surgicalinstruments and, more particularly, to subcutaneous ultrasonicdissection instruments incorporating pharmacological delivery.

BACKGROUND OF THE INVENTION

[0003] Implantable cardiac rhythm management systems have been used asan effective treatment for patients with serious arrhythmias. Thesesystems typically include one or more leads and circuitry to sensesignals from one or more interior and/or exterior surfaces of the heart.Such systems also include circuitry for generating electrical pulsesthat are applied to cardiac tissue at one or more interior and/orexterior surfaces of the heart. For example, leads extending into thepatient's heart are connected to electrodes that contact the myocardiumfor sensing the heart's electrical signals and for delivering pulses tothe heart in accordance with various therapies for treating arrhythmias.

[0004] Implantable cardioverter/defibrillators (ICDs) have been used asan effective treatment for patients with serious cardiac arrhythmias.For example, a typical ICD includes one or more endocardial leads towhich at least one defibrillation electrode is connected. Such ICDs arecapable of delivering high-energy shocks to the heart, interrupting theventricular tachyarrythmia or ventricular fibrillation, and allowing theheart to resume normal sinus rhythm. ICDs may also include pacingfunctionality.

[0005] Although ICDs are very effective at preventing Sudden CardiacDeath (SCD), most people at risk of SCD are not provided withimplantable defibrillators due to the difficulty of the implantationprocedure. The primary reasons for this unfortunate reality include thelimited number of physicians qualified to perform transvenouslead/electrode implantation, a limited number of surgical facilitiesadequately equipped to accommodate such cardiac procedures, and alimited number of the at-risk patient population that can safely undergothe required endocardial or epicardial lead/electrode implant procedure.

[0006] For reasons stated above, and for other reasons that will becomeapparent to those skilled in the art upon reading the presentspecification, there is a need for systems and methods that improvedelivery of cardiac sensing and therapy leads/electrodes. There is aparticular need for tools and techniques that facilitate implantation ofsuch systems. The present invention fulfills these and other needs, andaddresses deficiencies in known systems and techniques.

SUMMARY OF THE INVENTION

[0007] The present invention is directed to ultrasonic subcutaneousdissection tools, methods and systems that, in general, provide accessfor deployment of subcutaneous electrodes, cans, and housings used incardiac monitoring, transthoracic defibrillation therapies,transthoracic pacing therapies, or a combination of the above.Embodiments of the present invention include ultrasonic subcutaneousdissection tools, and systems that include pharmacological deliveryduring dissection.

[0008] According to one embodiment, an ultrasonic dissection tool of thepresent invention includes a handle having a proximal end and a distalend, a transducer adapted to produce ultrasonic energy, and an elongateddissecting member having a proximal end and a distal end. The elongateddissecting member extends from the distal end of the transducer. A fluidchannel system extends from at least the proximal end of the elongateddissecting member to the distal end of the elongated dissecting member.The fluid channel system terminates in a port system. The port systemmay include one or more apertures, one or more channels, and be adaptedto transport fluids such as, for example, irrigation fluids, fluidshaving analgesics, antibiotics, and combinations of fluids and agents.The fluid dispensed through the fluid channel system is typically aliquid, but may alternatively be a gas. A system incorporatingdissection tools in accordance with the present invention may includefluid storage, a pump, and tubing for fluid delivery.

[0009] Another embodiment of the present invention is directed to asheath removably surrounding the dissector. The sheath may be left inplace after removal of the dissector to facilitate electrode deliveryand implantation. The sheath may thereafter be stripped out of thedissection path to fix the electrode lead, such as through the use of apeel-away feature.

[0010] Another embodiment of the present invention provides a method ofdissection. The method of dissecting subcutaneous tissue in accordancewith the present invention is directed to ultrasonically dissectingsubcutaneous tissue with the dissection tool, and delivering a fluidfrom the dissection tool during dissection. The fluid delivered mayinclude agents that provide analgesia, hemostasis, bacterial fightingand infection fighting, and/or flushing of debris. The dissection methodmay include steps of following the subcutaneous plane for dissectionalong the curvature of the rib cage, for example.

[0011] The above summary of the present invention is not intended todescribe each embodiment or every implementation of the presentinvention. Advantages and attainments, together with a more completeunderstanding of the invention, will become apparent and appreciated byreferring to the following detailed description and claims taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIGS. 1A and 1B are views of a transthoracic cardiac sensingand/or stimulation device as implanted in a patient;

[0013]FIG. 2A is a perspective view of a subcutaneous dissection systemin accordance with the present invention;

[0014]FIG. 2B is a perspective view of another subcutaneous dissectionsystem in accordance with the present invention;

[0015]FIG. 3A is a plan view of an ultrasonic dissector in accordancewith the present invention;

[0016]FIG. 3B is a magnified sectional view bisecting the distal end ofan ultrasonic dissector in accordance with the present invention;

[0017]FIG. 3C is a magnified perspective view of the distal end of anultrasonic dissector in accordance with the present invention;

[0018]FIG. 4 is a magnified sectional view bisecting the distal end ofan ultrasonic dissector in accordance with the present invention; and

[0019]FIG. 5 is a section view of the elongated dissecting member of anultrasonic dissector having a surrounding sheath in accordance with thepresent invention.

[0020] While the invention is amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail below. It is to beunderstood, however, that the intention is not to limit the invention tothe particular embodiments described. On the contrary, the invention isintended to cover all modifications, equivalents, and alternativesfalling within the scope of the invention as defined by the appendedclaims.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

[0021] In the following description of the illustrated embodiments,references are made to the accompanying drawings, which form a parthereof, and in which is shown by way of illustration various embodimentsin which the invention may be practiced. It is to be understood thatother embodiments may be utilized, and structural and functional changesmay be made without departing from the scope of the present invention.

[0022] A device in accordance with the present invention may include oneor more of the features, structures, methods, or combinations thereofdescribed herein below. For example, a subcutaneous ultrasonic dissectoror dissection method may be implemented to include one or more of theadvantageous features and/or processes described below. It is intendedthat such a dissection device or method need not include all of thefeatures and functions described herein, but may be implemented toinclude selected features and functions that provide for uniquestructures and/or functionality.

[0023] In general terms, a dissection tool of the present invention maybe used to facilitate implantation of a subcutaneous cardiac monitoringand/or stimulation device. One such device is an implantabletransthoracic cardiac sensing and/or stimulation (ITCS) device that maybe implanted under the skin in the chest region of a patient. The ITCSdevice may, for example, be implanted subcutaneously such that all orselected elements of the device are positioned on the patient's front,back, side, or other body locations suitable for sensing cardiacactivity and delivering cardiac stimulation therapy. It is understoodthat elements of the ITCS device may be located at several differentbody locations, such as in the chest, abdominal, or subclavian regionwith electrode elements respectively positioned at different regionsnear, around, in, or on the heart. A dissection tool and methodology ofthe present invention may be used to provide electrode and device accessat various subcutaneous body locations.

[0024] The primary housing (e.g., the active or non-active can) of theITCS device, for example, may be configured for positioning outside ofthe rib cage at an intercostal or subcostal location, within theabdomen, or in the upper chest region (e.g., subclavian location, suchas above the third rib). In one implementation, one or more electrodesmay be located on the primary housing and/or at other locations about,but not in direct contact with the heart, great vessel or coronaryvasculature. In another implementation, one or more electrodes may belocated in direct contact with the heart, great vessel or coronaryvasculature, such as via one or more leads implanted by use ofconventional transvenous delivery approaches. In another implementation,for example, one or more subcutaneous electrode subsystems or electrodearrays may be used to sense cardiac activity and deliver cardiacstimulation energy in an ITCS device configuration employing an activecan or a configuration employing a non-active can. Electrodes may besituated at anterior and/or posterior locations relative to the heart.

[0025] Referring now to FIGS. 1A and 1B of the drawings, there is showna configuration of an ITCS device implanted in the chest region of apatient at different locations by use of a dissection tool of thepresent invention. In the particular configuration shown in FIGS. 1A and1B, the ITCS device includes a housing 102 within which various cardiacsensing, detection, processing, and energy delivery circuitry may behoused. The housing 102 is typically configured to include one or moreelectrodes (e.g., can electrode and/or indifferent electrode). Althoughthe housing 102 is typically configured as an active can, it isappreciated that a non-active can configuration may be implemented, inwhich case at least two electrodes spaced apart from the housing 102 areemployed. An ITCS system according to this approach is distinct fromconventional approaches in that it is preferably configured to include acombination of two or more electrode subsystems that are implantedsubcutaneously in the anterior thorax.

[0026] In the configuration shown in FIGS. 1A and 1B, a subcutaneouselectrode 104 may be positioned under the skin in the chest region andsituated distal from the housing 102. The subcutaneous and, ifapplicable, housing electrode(s) may be positioned about the heart atvarious locations and orientations, such as at various anterior and/orposterior locations relative to the heart. The subcutaneous electrode104 is electrically coupled to circuitry within the housing 102 via alead assembly 106. One or more conductors (e.g., coils or cables) areprovided within the lead assembly 106 and electrically couple thesubcutaneous electrode 104 with circuitry in the housing 102. One ormore sense, sense/pace or defibrillation electrodes may be situated onthe elongated structure of the electrode support, the housing 102,and/or the distal electrode assembly (shown as subcutaneous electrode104 in the configuration shown in FIGS. 1A and 1B).

[0027] In one configuration, the lead assembly 106 is generally flexibleand has a construction similar to conventional implantable, medicalelectrical leads (e.g., defibrillation leads or combineddefibrillation/pacing leads). In another configuration, the leadassembly 106 is constructed to be somewhat flexible, yet has an elastic,spring, or mechanical memory that retains a desired configuration afterbeing shaped or manipulated by a clinician. For example, the leadassembly 106 may incorporate a gooseneck or braid system that may bedistorted under manual force to take on a desired shape. In this manner,the lead assembly 106 may be shape-fit to accommodate the uniqueanatomical configuration of a given patient, and generally retains acustomized shape after implantation. Shaping of the lead assembly 106according to this configuration may occur prior to, and during, ITCSdevice implantation.

[0028] In accordance with a further configuration, the lead assembly 106includes a rigid electrode support assembly, such as a rigid elongatedstructure that positionally stabilizes the subcutaneous electrode 104with respect to the housing 102. In this configuration, the rigidity ofthe elongated structure maintains a desired spacing between thesubcutaneous electrode 104 and the housing 102, and a desiredorientation of the subcutaneous electrode 104/housing 102 relative tothe patient's heart. The elongated structure may be formed from astructural plastic, composite or metallic material, and includes, or iscovered by, a biocompatible material. Appropriate electrical isolationbetween the housing 102 and the subcutaneous electrode 104 is providedin cases where the elongated structure is formed from an electricallyconductive material, such as metal.

[0029] In one configuration, the rigid electrode support assembly andthe housing 102 define a unitary structure (i.e., a singlehousing/unit). The electronic components and electrodeconductors/connectors are disposed within or on the unitary ITCS devicehousing/electrode support assembly. At least two electrodes aresupported on the unitary structure near opposing ends of thehousing/electrode support assembly. The unitary structure may have anarcuate or angled shape, for example.

[0030] According to another configuration, the rigid electrode supportassembly defines a physically separable unit relative to the housing102. The rigid electrode support assembly includes mechanical andelectrical couplings that facilitate mating engagement withcorresponding mechanical and electrical couplings of the housing 102.For example, a header block arrangement may be configured to includeboth electrical and mechanical couplings that provide for mechanical andelectrical connections between the rigid electrode support assembly andhousing 102. The header block arrangement may be provided on the housing102 or the rigid electrode support assembly. Alternatively, amechanical/electrical coupler may be used to establish mechanical andelectrical connections between the rigid electrode support assembly andthe housing 102. In such a configuration, a variety of differentelectrode support assemblies of varying shapes, sizes, and electrodeconfigurations may be made available for physically and electricallyconnecting to a standard ITCS device.

[0031] It is noted that the electrodes and the lead assembly 106 may beconfigured to assume a variety of shapes. For example, the lead assembly106 may have a wedge, chevron, flattened oval, or a ribbon shape, andthe subcutaneous electrode 104 may include a number of spacedelectrodes, such as an array or band of electrodes. Moreover, two ormore subcutaneous electrodes 104 may be mounted to multiple electrodesupport assemblies 106 to achieve a desired spaced relationship amongstthe subcutaneous electrodes 104.

[0032] Accordingly, dissection tools of the present invention may beshaped to provide appropriate access for specific electrodes or familiesof electrodes, electrode support assemblies, and/or leads. For example,a dissection tool of the present invention may be adapted to provide achevron shaped tunnel, possibly having a particular radius of curvature,in order to facilitate placement of a semi-rigid chevron shaped curvedelectrode. Likewise, a kit may be assembled having particular shapedelectrodes along with particular dissectors adapted for placement of thespecific electrodes. The physician may use a number of specificallyshaped dissection tools during an implant procedure. Depending on theconfiguration of a particular ITCS device, a delivery systemincorporating drug/fluid delivery may advantageously be used tofacilitate proper placement and orientation of the ITCS device housingand subcutaneous electrode(s).

[0033] Examples of tools, aspects of which may be incorporated into adissecting tool in accordance with the present invention, are disclosedin commonly owned U.S. Pat. No. 5,300,106, U.S. patent application Ser.No. 10/625,826 entitled “Tunneling tool with Subcutaneous TransdermalIllumination,” filed on Jul. 23, 2003 under Attorney Docket No.GUID.619PA, and U.S. patent application Ser. No. 10/625,833 entitled“Subcutaneous Dissection Tool Incorporating Pharmacological AgentDelivery,” filed on Jul. 23, 2003 under Attorney Docket No. GUID.614PA,which are hereby incorporated herein by reference. These and otherconventional delivery devices may advantageously be modified toincorporate a drug/fluid delivery capability and other structural andfunctional features as described herein. An improved ITCS dissecting anddevice delivery tool in accordance with the present invention isdescribed below.

[0034] Embodiments of a delivery system according to the presentinvention are illustrated in FIGS. 2A and 2B. Referring to FIG. 2A, asubcutaneous dissection system 250 includes an ultrasonic generator 256and a subcutaneous ultrasonic dissector 290 including a transducer 281,a handle 260 and an elongated dissecting member 280. The generator 256is electrically coupled to the transducer 281 via a cable 221. A fluid,such as a pharmacological agent 272, is stored in a reservoir 270, andmay be pumped by a pump 255 through a tubing 257 and delivered to tissuethrough a port system 282 of the subcutaneous ultrasonic dissector 290.

[0035] The pump 255 and generator 256 may be turned off and on using acontrol 275. The control 275 may be connected to the pump 255 andgenerator 256 by, for example, wiring 258. The control 275 may be, forexample, a switch, a foot pedal, or other actuator capable ofcontrolling the generator 256 and pump 255.

[0036] It may also be desirable to provide aspiration with thesubcutaneous dissection system 250. An aspirant reservoir 270A mayoptionally be associated with the ultrasonic dissector 290. The aspirantreservoir 270A may be fluidly connected with the pump 255, whereby thepump 255 operates in a first mode to pump fluid into the subcutaneousultrasonic dissector 290, and operates in a second mode to aspirateaspirant from the subcutaneous ultrasonic dissector 290. The aspirantreservoir 270A may also be connected to a vacuum system or other meansof providing aspiration as is known in the art.

[0037]FIG. 2B is a perspective view of another subcutaneous dissectionsystem in accordance with the present invention. In FIG. 2B, theaspirant reservoir 270A is connected to the subcutaneous ultrasonicdissector 290 through a valve 273. The pump 255 may also be fluidlyconnected to the subcutaneous ultrasonic dissector 290 through the valve273. The valve 273 may be adapted to alternate between aspiration,irrigation, and/or fluid pumping modes. The tubing 257 may be a singlelumen tubing, a multiple lumen tubing, or a multiple tube arrangement.The valve 273 may be adapted to provide simultaneous aspiration andpumping through a multiple lumen or multiple tubing arrangement. Thevalve 273 may be operated via actuation of the control 275.

[0038] The control 275 may be connected to the generator 256, the pump255 and/or the valve 273 by, for example, wiring 258. The control 275may be, for example, a switch, a foot pedal, or other actuator capableof controlling the generator 256, pump 255 and/or the valve 273. Thecontrol 275 may be, for example, a switch located on the handle 260, afoot pedal located within reach of a clinician's feet, or implementedwithin the pump 255 as a voice-activated solenoid actuated valve.

[0039] The pump 255 delivers the pharmacological agent 272 throughtubing 257. Although the tubing 257 is illustrated as an elementseparate from the subcutaneous ultrasonic dissector 290, it iscontemplated that some or all of the components illustrated in FIGS. 2Aand 2B may be enclosed within the subcutaneous ultrasonic dissector 290,for example, within the handle 260. It is also contemplated that thetubing 257 may enter the subcutaneous ultrasonic dissector 290 distal tothe handle 260, such as, for example, directly to the elongateddissecting member 280. It is further contemplated that the subcutaneousultrasonic dissector 290 could be adapted to interface to a roboticsurgical system by, for example, adapting the handle 260 to interfacewith a robotic arm instead of a clinician's hand.

[0040] Referring to FIGS. 2A and 2B, the pharmacological agent 272 mayinclude any agent helpful to the efficacy of the subcutaneous ultrasonicdissector 290. The pharmacological agent 272 may include, for example,saline solution, phosphated buffer solution, an analgesic, anantibiotic, a hemostatic agent, an anti-inflammatory, or other usefuldrug or fluid.

[0041] For example, a non-exhaustive, non-limiting list of analgesicsincludes both fast acting and long acting drugs. PROCAINE, for example,may provide fast acting pain relief. BUPIVACAINE, LIDOCAINE, andMAPRIVACAINE, for example, may provide long acting pain relief.

[0042] A non-limiting example of a useful antibiotic is VANCOMYCIN, anda non-limiting example of an antiseptic in accordance with the presentinvention is CEFALOZIN. VANCOMYCIN may be used for the treatment ofinfection, and CEFALOZIN may be used to prevent possible infection alongthe dissection path.

[0043] A non-exhaustive, non-limiting list of anti-inflammatory drugsincludes the glucocorticoid family of drugs (steroids). Usefulanti-inflammatory drugs include DEXAMETHASONE, BETAMETHASONE, andIBUPROFIN, for example.

[0044] A non-exhaustive, non-limiting list of agents that may improvethe electrical properties of dissected tissue includes theglucocorticoid family of drugs, including, for example, DEXAMETHASONEand BETAMETHASONE. These and other candidate drugs may provide for lowerchronic defibrillation and pace/sense thresholds for subcutaneouslead/electrode systems. These and other fluids and/or drugs may bedelivered individually or in desired combinations prior to, during, andafter dissection for purposes of enhancing patient comfort, fightinginfections, lowering defibrillation thresholds, and/or chemicallytreating other conditions.

[0045] In FIGS. 2A and 2B, the elongated dissecting member 280 isillustrated as a straight member. However, it is contemplated that theelongated dissection member 280 may have any useful shape. For example,the elongated dissecting member 280 may be curved in one or more planes,and may have a simple or complex curvature defined by one or more radii.The radii of curvature may range from about 25 cm to about 2.5 cm, forexample.

[0046] The elongated dissecting member 280 may, for example, have apre-defined curvature to properly position an ITCS electrode relative tothe can for proper location of the electric field relative to apatient's heart. The elongated dissecting member 280 may also, oralternately, have a pre-defined curvature that may easily follow thecurvature of the rib cage for proper dissection. It is contemplated thatany combination of predefined shapes may be utilized in the presentinvention. It is also contemplated that multiple curvatures may also beused. For example, a first curvature in a first direction may help theultrasonic dissector conform to the curvature of the rib cage, while asecond curvature in a second direction may be useful for optimallylocating the leads and can relative to the heart or other anatomy. Asmentioned above, the curvature of the elongated dissecting member 280may be defined by a single radius, or by multiple radii or varyingradii.

[0047]FIGS. 3A through 3C illustrate various embodiments of subcutaneousultrasonic dissector 290 and dissecting element 280 in accordance withthe present invention. FIG. 3A illustrates an embodiment of thesubcutaneous ultrasonic dissector 290 having the ultrasonic transducer281 proximal of the elongated dissecting element 280, an arrangementsuitable for low-frequency high-power applications such as, for example,below 200 kilohertz, and particularly within the range of about 20kilohertz to about 50 kilohertz.

[0048] The ultrasonic transducer 281 converts electrical energy from thegenerator 256 (shown in FIGS. 2A and 2B) to mechanical motion of theelongated dissecting member 280. The mechanical motion disrupts tissueas the elongated dissecting member 280 is inserted, facilitating thedissection. For example, the elongated dissecting member 280 may liquefyadipose tissue, creating a tunnel for subsequent lead placement.Transducers of this type are known in the art, such as, for example,U.S. Pat. No. 5,449,370, hereby incorporated herein by reference. Themechanical motion is also useful for driving the pharmacological agentinto tissue, a process often referred to as sonophoresis.

[0049]FIG. 3B illustrates an embodiment of the elongated dissectingelement 280 having the ultrasonic transducer 281 at the distal end, anarrangement particularly suitable for high-frequency high-powerapplications. The ultrasonic transducer 281 converts electrical energyfrom the generator 256 to pressure-waves that emanate from theultrasonic transducer 281. This arrangement is effective for frequenciesabove 200 kilohertz and in megahertz ranges, particularly in the rangeof about 1 megahertz to about 4 megahertz. Transducers of this type areknown in the art, such as, for example, published US Patent Applicationnumber US20030040698 and U.S. Pat. No. 6,500,121 B1, which are herebyincorporated herein by reference. The pressure waves, similarly to themechanical motion described above, are useful for sonophoresis.

[0050] Referring to FIGS. 3A and 3B, the ultrasonic transducer 281 maybe driven continuously, or may also be modulated or interrupted. Forexample, the ultrasonic transducer 281 may be driven at a duty cyclehaving a first amplitude for a portion of the cycle, and havingeffectively zero amplitude for the remainder of the cycle. Theultrasonic transducer 281 may also be driven at varying amplitudes overa cycle in a modulated mode, such as, for example, having a saw-toothmodulation envelope or other envelopes as is known in the art. Aconvenient measure of system power is the power transferred from thegenerator 256 to the transducer 281. System power may vary between about1 Watt and about 200 Watts.

[0051]FIG. 3C is a magnified perspective view of the distal end of theelongated dissecting element 280 shown in FIGS. 2A and 2B. A port system282 is depicted as having an axial aperture 286 and a number of lateralapertures 283, 284, and 285. Depiction of the apertures 283, 284, 285and 286 is for purposes of clarity of explanation, and not oflimitation. It is contemplated that a single aperture, or any number ofapertures, may be located on the elongated dissecting element 280 at anylocation.

[0052] For example, a single or series of apertures may be locatedproximally from the distal end of the elongated dissecting member 280 toprovide a pharmacological agent or other fluid anywhere along the pathof dissection. If, for example, an analgesic is delivered duringdissection, it may be efficacious to provide a number of ports of portsystem 282 at the distal end of the ultrasonic dissector to ease thepain of dissection, but also to deliver incremental amounts of analgesicalong the length of the elongated dissecting member 280 as theultrasonic dissector advances into tissue.

[0053] The pharmacological agent 272 (shown in FIGS. 2A and 2B) may bedelivered continuously from the port system 282 during dissection. It isalso contemplated that the pharmacological agent 272 may be delivered inbolus fashion at time intervals, or only delivered on demand throughactuation of the control 275. For example, the pharmacological agent 272may be delivered when a clinician desires to flush out debris from thedissection path, and may deliver saline solution to remove the debris.As the pharmacological agent 272 is delivered from the subcutaneousultrasonic dissector 290, the ultrasonic energy may drive the agent intothe tissue surrounding the elongated dissecting member 280.

[0054]FIG. 4 is a magnified sectional view bisecting the distal endillustrated in FIG. 3C. In FIG. 4, the port system 282 is illustrated asincluding a single channel 287 terminating in the port system 282.Apertures 283, 284, 285, and 286 are fluidly coupled to the channel 287via branch channels to provide an exit point for a pharmacological orother fluid. The channel 287 may be, for example, molded or machinedfrom Titanium, such as, for example, Ti6Al4V or other suitable material.For example, the elongated dissecting element 280 may be machined from asuitable material, and include one or more channels 287. The elongateddissecting member 280 may include a number of channels 287 terminatingin a number of port systems 282 to provide delivery of a variety offluids and/or pharmacological agents 272, and/or to provide delivery offluids and/or pharmacological agents 272 to different locations alongthe length of the elongated dissecting member 280.

[0055] Referring now to FIG. 5, a sheath 500 may be provided to surroundthe elongated dissecting member 280. The sheath 500 may extend along aportion of, or the entire length of, the elongated dissecting member280. As dissection occurs, the sheath 500 may be inserted along thedissection path. Alternatively, the sheath 500 may be inserted after thedissection procedure is completed. Upon completion of the dissectionprocedure, the subcutaneous ultrasonic dissector 290 may be removed fromthe patient's body. After removal of the subcutaneous ultrasonicdissector 290, the sheath 500 may be left in-place, to provide a guidefor placement of electrodes and/or the ITCS housing. After placement ofthe electrodes and/or housing, the sheath 500 may be stripped out,leaving the electrodes properly positioned.

[0056] In one embodiment, the sheath 500 may include one or morelongitudinal pre-stress lines extending between a distal end and aproximal end of the sheath 500. The sheath 500 may optionally include asheath handle. The pre-stress line provides for a peel-away or tear-awaysheath 500 that facilitates extraction of the sheath 500 from the body.If the sheath 500 is provided with a sheath handle, the sheath handle ispreferably separable into at least two sections such that sheath handleseparation splits the sheath along the longitudinal pre-stress line atthe proximal end of the sheath 500. The sheath 500 (with or without asheath handle) splits along the longitudinal pre-stress line upon sheathretraction in a proximal direction.

[0057] Various modifications and additions can be made to the preferredembodiments discussed hereinabove without departing from the scope ofthe present invention. Accordingly, the scope of the present inventionshould not be limited by the particular embodiments described above, butshould be defined only by the claims set forth below and equivalentsthereof.

What is claimed is:
 1. A method of dissecting subcutaneous tissue,comprising: ultrasonically dissecting subcutaneous tissue to create apath in the subcutaneous tissue; delivering a fluid to the subcutaneoustissue during dissection; and impelling the fluid into tissue usingsonophoresis.
 2. The method of claim 1, wherein the dissection isperformed only in a subcutaneous tissue plane.
 3. The method of claim 1,wherein a plane of dissection follows a curvature of the rib cage. 4.The method of claim 1, further comprising delivering one or moreelectrodes into the subcutaneous tissue path.
 5. The method of claim 4,further comprising delivering a housing into the subcutaneous tissuepath, wherein the housing matingly connects with the one or moreelectrodes.
 6. The method of claim 1, further comprising advancing asheath into the subcutaneous tissue path.
 7. The method of claim 6,wherein the sheath is advanced into the subcutaneous tissue path duringsubcutaneous tissue dissection.
 8. The method of claim 6, furthercomprising delivering one or more electrodes into the subcutaneoustissue path via the sheath.
 9. The method of claim 6, further comprisingdelivering a lead to which one or more electrodes are respectivelycoupled into the subcutaneous tissue path via the sheath.
 10. The methodof claim 1, wherein delivering the fluid comprises impelling the fluidfrom a single ultrasonic dissection tool location or from multipledissection tool locations.
 11. The method of claim 1, wherein the fluidcomprises an irrigation fluid.
 12. The method of claim 1, wherein thefluid comprises a pharmacological agent.
 13. The dissection system ofclaim 1, wherein the fluid comprises an analgesic or an anesthetic. 14The dissection system of claim 1, wherein the fluid comprises anantibiotic or an antiseptic.
 15. The method of claim 1, wherein thefluid comprises an anti-inflammatory agent or an agent that promoteshemostasis.
 16. A dissection tool, comprising: a handle; an ultrasonictransducer connected to the handle, the ultrasonic transducer having aproximal end and a distal end, the proximal end of the ultrasoundtransducer coupled to the handle; an elongated dissecting member havinga proximal end and a distal end, the elongated dissecting memberextending from the distal end of the ultrasonic transducer; and a fluidchannel system extending from at least the proximal end of the elongateddissecting member to the distal end of the elongated dissecting member,the fluid channel system terminating in a port system.
 17. Thedissection tool of claim 16, wherein the ultrasonic transducer is drivenby a signal at one or more frequencies ranging between about 20kilohertz and about 200 kilohertz.
 18. The dissection tool of claim 16,wherein the ultrasonic transducer is driven by a signal at one or morefrequencies ranging between about 20 kilohertz and about 50 kilohertz.19. The dissection tool of claim 16, wherein the ultrasonic transduceris driven by a pulsed electrical signal having a duty cycle rangingbetween about 10% and 100%.
 20. The dissection tool of claim 16, whereinthe ultrasonic transducer is driven at a power level ranging betweenabout 1 watt and about 200 watts.
 21. The dissection tool of claim 16,wherein the ultrasonic transducer is mounted in the handle of thedissection tool.
 22. The dissection tool of claim 16, wherein the portsystem comprises a plurality of apertures.
 23. The dissection tool ofclaim 16, wherein the fluid channel system is adapted to transport anirrigation fluid.
 24. The dissection tool of claim 16, wherein the fluidchannel system is adapted to transport a pharmacological agent.
 25. Thedissection tool of claim 16, wherein the fluid channel system is adaptedto transport an analgesic or an anesthetic.
 26. The dissection tool ofclaim 16, wherein the fluid channel system is adapted to transport anantibiotic or an antiseptic.
 27. A dissection tool, comprising: a handlehaving a proximal end and a distal end; an elongated dissecting memberhaving a proximal end and a distal end, the elongated dissecting memberextending from the distal end of the handle; an ultrasonic transducerprovided at the distal end of the elongated dissecting member; and afluid channel system extending from at least the proximal end of theelongated dissecting member to the distal end of the elongateddissecting member, the fluid channel system terminating in a portsystem.
 28. The dissection tool of claim 27, wherein the ultrasonictransducer is driven by a signal at one or more frequencies rangingbetween about 0.2 megahertz and about 3 megahertz.
 29. The dissectiontool of claim 27, wherein the ultrasonic transducer is driven by apulsed electrical signal having a duty cycle ranging between about 10%and 100%.
 30. The dissection tool of claim 27, wherein the ultrasonictransducer is driven at a power level ranging between about 1 watt andabout 200 watts.
 31. The dissection tool of claim 27, wherein the portsystem comprises a plurality of apertures.
 32. The dissection tool ofclaim 27, wherein the fluid channel system is adapted to transport apharmacological agent.
 33. The dissection tool of claim 27, wherein thefluid channel system is adapted to transport an analgesic or ananesthetic.
 34. The dissection tool of claim 27, wherein the fluidchannel system is adapted to transport an antibiotic or an antiseptic.35. The dissection tool of claim 27, further comprising an aspirationchannel extending from at least the proximal end of the elongateddissecting member to the distal end of the elongated dissecting member,the aspiration channel adapted to aspirate debris.
 36. A method ofdissecting subcutaneous tissue, comprising: providing an ultrasonicdissection tool having a fluid delivery system; dissecting subcutaneoustissue with the ultrasonic dissection tool to create a path in thesubcutaneous tissue; and delivering a fluid from the dissection toolduring subcutaneous tissue dissection via a fluid delivery system. 37.The method of claim 36, further comprising aspirating debris from thepath.
 38. The method of claim 36, wherein the ultrasonic dissection toolcomprises an ultrasonic transducer that is driven at one or morefrequencies ranging between about 20 kilohertz and about 200 kilohertz.39. The method of claim 36, wherein the ultrasonic dissection toolcomprises an ultrasonic transducer that is driven at one or morefrequencies of less than about 50 kilohertz.
 40. The method of claim 36,wherein the ultrasonic dissection tool comprises an ultrasonictransducer that is driven at one or more frequencies ranging betweenabout 0.2 megahertz and about 3 megahertz.
 41. The method of claim 36,further comprising ultrasonically disrupting tissue or other debris inthe path of the dissection tool as the dissection tool is advancedthrough the subcutaneous tissue using ultrasonic vibration.
 42. Themethod of claim 36, further comprising ultrasonically liquifying tissuein the path of the dissection tool as the dissection tool is advancedthrough the subcutaneous tissue using ultrasonic vibration therebycreating the path.
 43. The method of claim 36, further comprisingultrasonically disrupting dissected tissue or other debris in the fluiddelivery system as the dissection tool is advanced through thesubcutaneous tissue using ultrasonic vibration.
 44. The method of claim36, wherein the ultrasonic transducer is driven by a pulsed electricalsignal having a duty cycle ranging between about 10% and 100%.
 45. Themethod of claim 36, further comprising delivering one or more electrodesinto the subcutaneous tissue path.
 46. The method of claim 45, furthercomprising delivering a housing into the subcutaneous tissue path,wherein the housing matingly connects with the one or more electrodes.47. The method of claim 45, further comprising advancing a sheath intothe subcutaneous tissue path.
 48. The method of claim 47, wherein thesheath is advanced into the subcutaneous tissue path during subcutaneoustissue dissection.
 49. The method of claim 47, further comprisingdelivering the one or more electrodes into the subcutaneous tissue pathvia the sheath.
 50. The method of claim 36, wherein delivering the fluidcomprises dispensing the fluid from a single ultrasonic dissection toollocation or from multiple dissection tool locations.
 51. The method ofclaim 36, wherein the ultrasonic transducer is driven at a power levelranging between about 1 watt and about 200 watts.
 52. The method ofclaim 36, wherein the dissection is performed only in a subcutaneoustissue plane.
 53. The method of claim 36, wherein a plane of dissectionfollows a curvature of the rib cage.
 54. The method of claim 36, furthercomprising ultrasonically disrupting tissue or other debris in the pathof the dissection tool as the dissection tool is advanced through thesubcutaneous tissue.
 55. The method of claim 36, further comprisingultrasonically disrupting dissected tissue or other debris in the fluiddelivery system as the dissection tool is advanced through thesubcutaneous tissue.
 56. The method of claim 36, wherein delivering thefluid comprises delivering an irrigation fluid.
 57. The method of claim36, wherein delivering the fluid comprises delivering a pharmacologicalagent.
 58. The method of claim 36, wherein delivering the fluidcomprises delivering an analgesic or an anesthetic.
 59. The method ofclaim 36, wherein delivering the fluid comprises delivering anantibiotic or an antiseptic.
 60. A dissection tool, comprising: anultrasonic transducer; means, coupled to the ultrasonic transducer, fordissecting subcutaneous tissue; and means for delivering a fluid throughor along the dissecting means and to tissue subject to dissection. 61.The dissection tool of claim 60, further comprising means forcontrollably supplying the fluid to the fluid delivering means.
 62. Thedissection tool of claim 60, further comprising means for aspiratingdebris from the dissected tissue.
 63. The dissection tool of claim 60,further comprising means for controllably activating the ultrasonictransducer.
 64. The dissection tool of claim 60, further comprisingmeans for impelling the fluid from the dissecting means and into thetissue subject to dissection.
 65. The dissection tool of claim 60,further comprising means for dispensing the fluid from the dissectingmeans and into the tissue subject to dissection.
 66. A dissectionsystem, comprising: a pump; a fluid reservoir adapted to provide a fluidto the pump; a tube; and a dissection tool comprising an elongateddissecting member, an ultrasonic transducer coupled to the elongateddissecting member, and a fluid channel system extending between proximaland distal ends of the elongated dissecting member, wherein the tubefluidly connects the dissection tool with the pump.
 67. The dissectionsystem of claim 66, wherein the ultrasonic transducer is driven by asignal at one or more frequencies ranging between about 20 kilohertz andabout 200 kilohertz.
 68. The dissection system of claim 66, wherein theultrasonic transducer is driven by a signal at one or more frequenciesof less than about 50 kilohertz.
 69. The dissection system of claim 66,wherein the ultrasonic transducer is driven by a signal at one or morefrequencies ranging between about 0.2 megahertz and about 3 megahertz.70. The dissection system of claim 66, wherein the ultrasonic transduceris driven by a pulsed electrical signal having a duty cycle rangingbetween about 10% and 100%.
 71. The dissection system of claim 66,wherein the ultrasonic transducer is driven at a power level rangingbetween about 1 watt and about 200 watts.
 72. The dissection system ofclaim 66, wherein the fluid channel system comprises a port system, theport system comprising a plurality of apertures.
 73. The dissectionsystem of claim 66, wherein the pump comprises a pump controlleractuatable by a clinician that controls dispensing of the fluid from thefluid reservoir to the dissection tool.
 74. The dissection system ofclaim 66, further comprising a sheath removably displaceable over theelongated dissecting member.
 75. The dissection system of claim 66,wherein the fluid comprises an irrigation fluid.
 76. The dissectionsystem of claim 66, wherein the fluid comprises a pharmacological agent.77. The dissection system of claim 66, wherein the fluid comprises ananalgesic or an anesthetic.
 78. The dissection system of claim 66,wherein the fluid comprises an antibiotic or an antiseptic.
 79. A methodof dissecting subcutaneous tissue, comprising: ultrasonically dissectingsubcutaneous tissue to create a path in the subcutaneous tissue;delivering a fluid to the subcutaneous tissue during subcutaneous tissuedissection; and impelling the fluid into the subcutaneous tissue viasonophoresis.
 80. The method of claim 79, wherein the fluid comprises anirrigation fluid.
 81. The method of claim 79, wherein the fluidcomprises a pharmacological agent.
 82. A method of dissectingsubcutaneous tissue, comprising: ultrasonically dissecting subcutaneoustissue to create a path in the subcutaneous tissue; and delivering apharmacological fluid to the subcutaneous tissue during subcutaneoustissue dissection.
 83. The method of claim 82, wherein thepharmacological fluid comprises an analgesic or an anesthetic.
 84. Themethod of claim 82, wherein the pharmacological fluid comprises anantibiotic or an antiseptic.